/Engine/Source/Runtime/Engine/Classes/Components/SkeletalMeshComponent.h
Enable or Disable AngularPositionDrive. If motor is in SLERP mode it will be turned on if either EnableSwingDrive OR EnableTwistDrive are enabled. In Twist and Swing mode the twist and the swing can be controlled individually.
void SetAllMotorsAngularPositionDrive ( bool bEnableSwingDrive, bool bEnableTwistDrive, bool bSkipCustomPhysicsType )